Dielectric Filter for Diffuse Light Reflection in Spectroscopy
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Solution Overview
Problem
In spectroscopic applications, particularly with diffusely scattering samples, there is a challenge in maximizing the intensity of incident light while minimizing exposure times and preventing light loss, especially in applications where sensitive equipment is limited or sample damage is a concern.
Innovation Solution
A method involving a delivery filter with specific reflection characteristics is used to direct incident light into a diffusely scattering sample, where the filter preferentially reflects diffusely scattered light back into the sample, reducing light loss and increasing intensity within the sample.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If incident light intensity is increased to improve spectral signal detection, then measurement sensitivity is improved, but sample damage risk increases
Solution Approach 1:
The filter is positioned specifically at the light entry point on the sample surface, creating a localized optical modification only where light enters. This allows enhanced light retention within the sample volume without exposing the entire sample to potentially damaging high intensities, as the filter selectively manages only the incident light pathway.
Solution Approach 2:
The delivery filter acts as an intermediary optical element between the light source and the sample. It mediates the interaction by selectively reflecting scattered light back into the sample while allowing incident light to pass through, thereby enhancing light utilization without directly exposing the sample to excessive intensities from the source.
2Productivity
If incident light intensity is increased to reduce exposure times, then productivity is improved, but light loss from the sample increases
Solution Approach 1:
The scattered light that would normally be lost and escape from the sample surface is converted into a beneficial resource by the filter. The filter reflects this otherwise wasted scattered light back into the sample, transforming energy loss into useful illumination that extends light path length and enhances spectral signal without requiring increased exposure times.
Solution Approach 2:
The filter enables continuous circulation of light within the sample by reflecting scattered light back into the sample volume. This creates a continuous useful action where light repeatedly interacts with the sample rather than escaping after a single pass, thereby maintaining high light utilization efficiency throughout the measurement process.
3Loss of energy
If a filter is added to reflect scattered light back into the sample, then light retention is improved, but device complexity increases
Solution Approach 1:
The optical system is segmented by separating the light delivery function from the light collection function. The delivery filter is positioned specifically at the light entry point to handle only the incident light pathway, while the rest of the optical system remains unchanged for collecting scattered light. This segmentation allows the filter to be added without redesigning the entire optical system.
Solution Approach 2:
The delivery filter extracts and manages only the specific function of handling incident light at the entry point, separating this function from the main optical system. This extraction allows the filter to be added as a discrete component that addresses light retention without complicating the overall optical design or requiring modifications to other system elements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the intensity of incident light within the sample, leading to improved spectral signal detection and reduced exposure times, effectively addressing the limitations of existing technologies in spectroscopic analysis.
Implementation Method 1
The filter has characteristics such that the light at the incident light wavelength which is diffusely scattered back from the sample to the filter at a wider range of angles of incidence than the incident beam is preferentially reflected back to the sample
Implementation Method 2
Some optical filter types, such as multi-layer dielectric filters have transmission and reflection characteristics which shift in wavelength, typically to shorter wavelengths, with increasing angle of incidence
Data Source
AI summary
The invention provides a technique for increasing the illumination intensity of probe light in a diffusely scattering sample without increasing the power of the probe beam. Generally, an optical filter is used which permits a collimated probe beam of light to pass through to the sample, but which reflects back towards the sample much of the backscattered scattered probe light emerging at a wider range of angles. In particular embodiments a collimated laser beam is delivered to the sample through a multi-layer dielectric filter covering a portion of the sample. The filter is transmissive to the laser light at normal incidence, but reflective at shallower angles of incidence characteristic of the backscattered light.